Methods for offshore drill stem testing

ABSTRACT

Methods for offshore drill stem testing from a floating vessel using a tester operated by upward and downward motion and coupled to a packer by a slip joint, the equipment being suspended in the well bore on upper and lower pipe string sections connected together by a slip joint. The tester and slip joints are balanced with respect to fluid pressure so that a sequence of free points observed on the rig weight indicator at the surface provides positive indications of operation of the tools.

FTP GlI Young et al.

TESTING METHODS FOR OFFSHORE DRILL STEM III, both of Houston; BenjaminP.

Nutter, Bellville, all of Tex.

tion, New York, NY.

Filed: Aug. 25, 1971 Appl. No.: 174,599

Related US. Application Data [56] References Cited UNITED STATES PATENTSInventors: David E. Young; James W. Kisling,

Assignee: Schlumberger Technology Corpora- Division of Ser. No. 42,374,June 1, 1970, Pat. No.

US. Cl. 166/250, 166/5 Int. Cl E2lb 47/06 Field of Search 166/.5, 250,152

Brown 166/.5 X

[ June 26, 1973 3,358,755 12/1967 Chisholm 166/152 X 3,451,475 6/1969Price 166/.5 3,646,995 3/1972 Manes et a1. 166/.5

Primary Examiner-David H. Brown Attorney- Ernest Archambeau, lr., DavidL, Moseley et al.

ABSTRACT 3 Claims, 6 Drawing Figures PATENTED JUN 2 8 I973 SHEEI' 1 [IF2 FIG] PATENTEDJUNZS ma F/G.4C

SNEH'ZUFZ METHODS FOR OFFSHORE DRILL STEM TESTING This is a division ofapplication Ser. No. 42,374, now US. Pat. No. 3,662,826, filed June 1,1970.

This invention relates generally to formation testing methods andapparatus, and more specifically to drill stem testing tools andprocedures adapted for use in testing wells from a floating vessel thatis subject to wave and tide action during testing operations.

In conventional drill stem testing of land based wells, or offshorewells equipped with fixed platforms, well known procedures and tools areused to isolate the formation interval to be tested and temporarily toenable a formation intersected by the borehole to produce fluids. Apacker and a tester valve are suspended in the well on a pipe string andthe packer is set to isolate the interval to be tested. Then by suitablemanipulation of the pipe string at the surface, the tester valve isopened and closed to obtain a sample of fluids while recorders obtainflow and shut-in pressure records from which certain valuable formationparameters can be determined.

Offshore drill stem tests performed from floating vessels, however,present a number of challenging problems requiring new approaches. Thevessel under the influence of wave and tide action is continuouslymoving vertically with respect to the formations being tested so thatpipe manipulations to operate the tools during a test may not be an easymatter. Moreover, many drill stem tests involve a repetitive sequence oftest tool manipulations to obtain adequate flow and shut-in pressuremeasurements. Accordingly, complete and positive control by the operatoris essential. It will be readily apparent that such control is made moredifficult due to the above-mentioned relative motion between the vesseland the location of the tools. Also in offshore operations, safety is anoverriding consideration due to the substantial risks to personnel andequipment should a blowout and fire occur, and for this reason it isgenerally considered to be undesirable to use tools requiring rotationbecause of therisks involved in rotating a pipe string that is underpressure. Moreover, test tools requiring pipe rotation for operation arenot as reliable as should be desired, because the operator may beuncertain as to how many of the pipe turns at the surface havecorrespondingly occurred at the tools.

Accordingly, the present invention provides a string of drill sterntesting equipment that is operated to initiate various phases of a testby raising and lowering the pipe string at the vessel. No rotation isrequired. In addition to being a safe system to operate, the requirementof only up and down motion makes possible the observation at the surfaceof data that will confirm that a predictable sequence of test periods orphases is in fact occuring at the formations. Relative longitudinalmovement between parts of the test equipment can be detected at thesurface by observing what are known as free points" on the rig weightindicator. A free point as used herein means a weight value or weightindicator reading that remains constant while the pipe is being liftedor lowered at the surface. The fact that the value remains constantmeans that a length of the pipe string corresponding to that weightvalue is hanging freely in the well bore, and such a free point will bedetected whenever there is relative longitudinal movement between a toolpart that is supported in the well bore and another tool part that issuspended by the pipe string. The occurrence of free points generallycan be predicted in advance and should remain constant during variousphases of a test provided that the formation testing tools and othersliding joints in the string of tools are arranged to be independent ofapplied fluid pressures.

In further accordance with the present invention, all sliding joints arebalanced with respect to applied fluid pressure, which means that suchjoints are constructed and arranged with transversely oriented surfacessubjected to fluid pressure in such a manner that applied pressures donot tend to either extend or close such joints. Thus it will beappreciated that the various weight values that are observed on theweight indicator at the surface during a test remain substantiallyconstant regardless of the pressure changes that occur during a test.Since the test tools are operated by longitudinal movement betweenparts, the observance of various free points at the surface providespositive indications of operation of the test tools.

An object of the present invention is to provide a new and improvedoffshore testing system that utilizes vertical motion of the drill pipeto operate tools that are independent of applied fluid pressures so thatdata which is physically observable at the surface provides positiveindications and assurance of operation of the tools.

Another object of the present invention is to provide a new and improveddrill stem testing system that includes a tester valve that can beoperated by vertical pipe motion without rotation and which is arrangedto be independent of applied pressures so that predictable free pointsobservable on the rig weight indicator at the surface are used toconfirm operation of the tools.

Yet another object of the present invention is to provide a new andimproved drill stem testing system that includes a test valve that isoperated by vertical motion of a pipe string, the tester being balancedso that the pipe string has a constant free point regardless of fluidpressure variations, and further including a bias means that responds tothe hydrostatic head of fluids in the well to apply upward force on thetester mandrel to assist in extension of the mandrel.

Still another object of the present invention is to provide a new andimproved drill stem testing system that includes a pressure balancedtester that is opened and closed by telescoping movement of a mandrelwithin a housing, the mandrel and housing enclosing an atmosphericchamber above an annular piston so that hydrostatic pressure assists inextending the mandrel, together with a slip joint having a significanttravel length connecting the tester to a well packer so that the freepoint for the joint is easily observed at the surface and the tester canbe operated without disturbing the packer.

These and other objects of the present invention are attained throughthe provision and use of a drill stem testing system comprising a majorpipe string that extends from the floating vessel into the well bore andis adapted to be suspended from a fixed point at the ocean floor. Themajor pipe string is connected by a slip joint to a minor pipe stringsuch as a length of drill collars having a known weight. The lower endof the minor string is coupled to the center mandrel of a testerassembly having a test valve that is opened and closed by upward anddownward motion of the mandrel within an outer housing. The major andminor strings are used to raise the mandrel, whereas the weight of theminor string is used to force the mandrel downwardly within the housing.

The mandrel and housing are provided respectively with piston andcylinder means with the upper face of the piston being subject to thepressure of fluids in the inner mandrel while the lower face of thepiston is subject to-the pressure of fluids in the surrounding wellannulus. The transverse area of the piston is sized to be equal to thetransverse area bounded by the outer peripheral surface of the mandrelin order to provide the balancing feature discussed above. A secondpiston and cylinder combination is also provided with only the lowerface of the piston being subject to the hydrostatic head of fluids inthe annulus, so that when the mandrel is forced downwardly the pressureacting on said lower face provides an upward force on the mandrel toassist in subseqently moving it upwardly. This force, called the biasforce, insures that the mandrel 'will return to its upper positionduring a sequence of operations in the absence of pipe weight, andindependently of the movement of other telescoping joints in the system.

The tester assembly including the pressure balance and bias is coupledto a well packer by a slip joint whose operation can be readily detectedat the surface by the observance of a lengthy free point on the rigweight indicator. The well packer can be any suitable type, butpreferably has a weight set packing element and an integral fluid bypassto equalize pressure when it is desired to terminate the test andretrieve the string of tools to the surface. A suitable anchor, such asslips and an expander, or a tail-pipe is used to properly locate thepacker in the borehole at a predetermined point above the interval to betested, and of course pressure recorders are provided to obtain apermanent record of the pressure changes that occur during the test.

The tester is operated by lifting and lowering the major and minor pipestrings, and indications of the operation of the tester are observableat the surface by monitoring the free points. As the majorstring islifted, for example, the first free point indication will shownextension of the slip joint between the strings and a second free pointmay be detected as the tester mandrel elevates to operate the valve. Inany event, the free point observed as the lower slip joint extendsprovides the operator with a well defined signal to release the brakeand lower the pipe strings. Even though a free point for the tester isnot detected, the existence of the bias force as previously describedinsures that the tester has extended before the free point of the lowerslip joint is observed. As the pipe strings are lowered, a reversesequence of free points will be seen. The lengths of the variouscomponents of the tool and pipe strings are spaced out such that whenthe major pipe string is suspended at the fixed point in the well bore,both slip joints are collapsed and the weight of the minor string isimposed on the tester to cause the mandrel to travel downwardly. Arepetitive sequence of such operation can be initiated to perform thedrill stem test with an optimum amount of safety and control.

The present invention has other objects and advantages that will becomemore clearly apparent in connection with the following detaileddescription on a preferred embodiment shown in the accompanying drawingsin which:

FIG. 1 is a somewhat schematic view of an offshore well having a stringof testing equipment in accordance with this invention suspended thereinfrom a floating vessel;

FIG. 2 is a longitudinal sectional view of a slip joint and safety valvecombination tool included in the string of tools shown in FIG. 1;

FIG. 3 is a longitudinal sectional view of one of the slip joints usedto provide free point indications at the surface;

FIGS. 4A and 4B are longitudinal sectional views of the tester valveassembly that is operated by up and down motion of the pipe string toalternately flow and shut-in the formation; and

FIG. 4C is a plan view of the channel and index system used in thetester to control the operating sequence thereof.

Referring initially to FIG. 1, a floating drilling vessel 10 isstationed over an offshore well 11 which transverses earth formations tobe tested. The well can be cased or open hole but is usually cased. Anunderwater wellhead assembly 12 is located on the ocean floor at the topof the well bore and is constituted by the usual casing head 13 and ablowout preventor stack 14. A riser 15 normally extends from the wellhead assembly 12 upwardly to the vessel 10. A pipe string 16 is coupledto the elevators 17 in the derrick 18 and extends downward through theriser 15 and the well head assembly l2 and into the well bore. A controlvalve assembly 19 of the type shown at page 3,730 of the 196869Composite Catalog of Oil Field Equipment and Services, can be connectedin the pipe string 16, the valve assembly having hanger surfaces 20which can he landed against a seat so that the pipe string 16 can besuspended from the assembly 12 during a test rather than from thetraveling block 17. The control valve assembly 19 contains suitableshut-off valves (not shown) which, in cooperation with the blowoutpreventor rams, can be closed to shut-in the well. The details of thewellhead assembly and the valve housing form no part of the presentinvention.

Positioned below the wellhead assembly 12 is a string of drill stemtesting tools including a slip joint and a safety valve combination-tool22, an upper slip joint 23, a string of drill collars 24, reversingvalves 25 and 26, a tester valve assembly 27 and a well packer 28coupled below the tester valve by a lower slip joint 29. If desired, thecombination tool 22 and the upper slip joint 23 can be separated byseveral sections of drill pipe. A perforated anchor pipe 30 is connectedbelow the packer 28, and a recorder carrier 31 with conventional insideand outside pressure recorders is attached to the lower end of theperforated anchor. The packer 28 functions to pack off and isolate aninterval of the well to be tested while the tester 27 is opened andclosed to alternately flow and shut-in the formations. The recordersmake a permanent chart of fluid pressure changes that occur during theflow and shut-in periods. Other conventional auxiliary equipment such asa jar and a safety joint can be included in the string between thepacker 28 and the lower slip joint 29 as desired. The reversing valves25 and 26 located immediately above the tester 27 are used to open thelower end of the pipe string 24 to the well annulus so that samples offluids can be reversed out at the termination of a test according totypical procedures. Of course the well bore 11 is illustrated as beinglined with a casing, however, it will be appreciated that in the eventthat the well is not cased, an open hole packer of the type shown inU.S. Pat. No. 2,657,751, dated Nov. 3, 1953, can be used together with atypical bypass valve.

Referring still to FIG. 1, the lower end of the pipe string 16 isconnected to a safety valve and slip joint assembly 22 that functions toshut-in the pipe string therebelow in the event that due to someunfortunate occurrence, the pipe string should be broken in two belowthe wellhead assembly 12. This tool is provided as a safety feature andis shown in detail in FIG. 2 as including an upper slip joint section 35and a lower valve section 36. The slip joint section 36 is formed by amandrel 37 that is slidably and non-rotatably disposed within an outerhousing 38, relative rotation being prevented by splines 39 and 40. Anannular piston 41 on the mandrel 37 can reciprocate within an internalannular chamber 42 in the housing 38, the wall of the chamber providinga cylinder that is sealed with respect to the mandrel by seals 43 and 44and with respect to the piston 41 by a seal 45. The transversecross-sectional area of the piston 41 is sized to be equal to the areacircumscribed by the outside surface of the mandrel 37 at the seal 43,and the upper face 46 of the piston is exposed to the pressure of fluidsinside the mandrel by ports 47. The lower face 48 of the piston 41 isexposed to the pressure of fluids in the well annulus by ports 49. Thusarranged, the slip joint is insensitive to pressure changes that occurwithin the joint, because an upward force on the mandrel 37 due togreater fluid pressure inside the mandrel is balanced or cancelled by adownward force due to the same pressure acting on the upper face 46 ofthe piston 41.

Turning now to the valve section 36 of the assembly 22, an annularsleeve member 50 is installed within the lower portion 51 of the housing38 with its outer periphery spaced inwardly from the inner wall of thelower portion 51 to provide an annular fluid passage space 52. A sleevevalve 53 fits slidably within the sleeve member 50 and is pressedtowardan upper position by a coil spring 54. In the upper position, the valve53 and sleeve 50 have lateral ports 55 and 56 that register with eachother to provide a fluid flow path through the housing and mandrel. Thesleeve valve 53 is sized to be engaged by the lower end surface 57 ofthe mandrel 37 and can be driven downwardly thereby to a positionwhereby upper and lower seals 58 and 59 span the ports 56 to block fluidcommunication. The through-bore 60 of the sleeve member 50 is closed bya knock-out plug or barrier assembly that includes a barrel 61 attachedto the sleeve member by a shear ring 62. The barrel has a downwardlyfacing valve seat 63 that is normally engaged by a spring-loaded ball 64to prevent fluid flow in an upward direction only. To remove thebarrier, a go-devil or bar (not shown) is dropped through the pipestring, and upon impact with the barrel 61, causes the member 62 toshear so that the barrier can fall down the pipe string 24.

The safety valve 22 is, in turn, connected to a balanced slip joint 23that is shown in detail in FIG. 3. The slip joint 23 has a hollow innermandrel 68 that is telescopically disposed within an outer housing 69.The upperend of the mandrel 68 is connected by a collar 70 to the lowerend of the safety valve 22, while the lower end of the housing 69 isconnected by a threaded pin 71 to the pipe string 24. External splines72 on the mandrel 68 mesh with internal spline grooves 73 in the housing69 to prevent relative rotation. The housing 69 has an internal annularchamber 74 that slidably receives an annular piston 75 on the mandrel68. Appropriate seals 76 and 77 seal off the chamber 74 at each end, anda seal 78 seals the piston 75 with respect to the inner wall of thechamber 69. The upper face 79 of the piston 75 is exposed to thepressure of fluids with the bore of the mandrel 68 via one or more ports80, and the lower face 81 of the piston is exposed to the pressure offluids in the well annulus via ports 82. The transverse area of thepiston 75 (bounded by the seals 76 and 78) is made equal to thetransverse area of the mandrel 68 (bounded by the seal 76). Thusarranged,

the slip joint is independent of the pressure changes that occur withinthe mandrel and housing as previously described with reference to theslip joint and safety valve combination tool 22.

The pipe string 24 is normally composed of a number of sections of drillcollars connected end-to-end. The total length of the string 24 ischosen to provide a certain amount of weight that is necessary forpurposes to be describedbelow. The lower end of the pipe string 24 canbe connected to conventional reverse circulating valves 25 and 26. Theupper valve 25 can be of the type having a side port closed by a plugthat can be released by pressure applied to the inside of the pipestring to enable reverse circulation by pressurizing the annulus. Thelower reversing valve 26 can be of the type shown in U.S. Pat. No.2,661,802, issued Dec. 8, 1953, the valve being operated by rotation ofthe pipe string to open ports and enable reversing out the fluidrecovery to the surface.

The lower end of the reversing valve 26 is connected to the upper end ofthe tester assembly 27. The tester assembly 27 shown in FIGS. 4A and 4B,is constituted by a control and indexing section 85, a delay section 86and a test valve and sample chamber section 87. The indexing, delay andvalved sample chamber sections are described generally in detail in U.S.Pat. No. 3,308,887, Nutter, dated Mar. 14, 1967, and basically include amandrel 90 that is slidable within a housing 91 between extended andretracted relative positions. An index sleeve 92 mounted on the housing91 is rotatable relative to both the housing 91 and the mandrel 90, andcarries an index pin 93 that follows in a channel system 94 depicted inplan view in FIG. 4C. The mandrel 90 has splines 95 that ride in splinegrooves 96 in the housing 91 to prevent relative rotation, so that asthe mandrel is moved successively upwardly and downwardly, the swivelsleeve 92 rotates due to the interengagement of the index pin 93 withinthe channel system 94. The mandrel 90 has lugs 98 that can engage inwardprojections 97 on the sleeve 92 only in certain relative rotationalpositions of the sleeve with respect to the mandrel. In all otherrelative positions, the lugs 98 pass through the spaces between theprojections 97 so that the lugs pass downwardly within the sleeve. Inthe running-in condition of the tester, the pin 93 is in the pocket Ashown in FIG. 4A and the mandrel 90 is extended relative to the housing91. To open the tester valve as will subsequently be described, themandrel 90 is lowered to the limit of its downward movement within thehousing 91, where the pin 93 is in the pocket B. During this relativelongitudinal movement, the mandrel lugs 98 bypass the projections 97. Toclose the tester valve, the mandrel 90 is elevated, and again the lugs98 bypass the projections 97 so that the mandrel moves to the upperlimit of its travel. The index pin 93 occupies position C. The mandrel90 is again lowered, but this time as the pin 93 moves to position D,the lugs 98 engage the projections 97 to limit downward movement. Thevalve is still closed and weight can be applied to the housing 91 andconsequently to the tools therebelow. The limit of downward movement ofthe mandrel 90 occurs when a shoulder 99 engages the top of the housing91, whereas the limit of upward movement is provided by engagement ofthe lugs 98 with a downwardly facing shoulder 100 on the housing.

The delay section 86 includes a metering sleeve 103 that is biasedupwardly against a shoulder 104 on the mandrel 90 by a spring 105. Themetering sleeve 103 is sized to provide a small clearance between itsoutside surface and the inner wall 106 of the housing 91. The sleeve 103further has grooves 107 or the like in its inner periphery to providefluid passage spaces. The upper end surface of the metering sleeve 103seats against the shoulder 104 during downward movement of the mandrel90 so that hydraulic fluid contained in a sealed chamber 108 above andbelow the sleeve must flow from below the sleeve to above the sleeve ata metered rate, thus providing a retarding or delaying action withrespect to downward movement. However, the mandrel 90 can be movedfreely upwardly because the fluid will push the sleeve 103 downwardlyaway from the shoulder 104 and fluid can bypass through the grooves 107from above the sleeve to below it. The wall surface 109 at the lowersection of the chamber 108 can be enlarged in diameter so that themetering action provided by the sleeve 103 is released as the mandrel 90nears the lower end portion of its travel.

The test valve and sample chamber section 87 comprises upper and lowervalve seals 112 and 113 on the mandrel 90 that engage spaced valve seats114 and 115 when the mandrel is extended or partially contracted, andare free of the seats when the mandrel is fully telescoped within thehousing 91. The annular space 116 in between the valve seats 1 14 and115 provides a flowthrough sample chamber, in that when the mandrel 90is in its lowermost position, fluids can flow upwardly from ports 117below a barrier 118 through the chamber 116 and through ports 119 abovethe barrier into the bore of the mandrel 90. However, when the mandrel90 is moved upwardly the seals 112 and 113 engage the seats 114 and 115simultaneously to trap a sample of fluids in the chamber 116. It will beappreciated that the valve is open only when the mandrel 90 iscompletely telescoped within the housing 91 and that when the mandrel isin the positions corresponding to positions C and D in FIG. 4C, thevalve is closed to shut-in the formations.

The foregoing tester assembly structure is fully described in theaforementioned Nutter patent, and the precise details form no part ofthe present invention. However, the foregoing broadly in combinationwith the following structure is believed to be unique in the art.Referring to FIG. 48, an extension 125 of the mandrel 90 is providedwith an annular piston 126 with the upper face of the piston exposed tothe pressure of fluids within the bore of the mandrel extension by ports127. A section 128 of the housing 91 provides a cylinder with aninwardly extending flange 129 sealed against the mandrel extension 125by a seal 130, and with the cylinder wall 131 sealed with respect to thepiston 126 by a seal 132. The lower face of the piston 126 is exposed tothe pressure of fluids in the annulus by ports 133. The transversecross-sectional area of the piston 126 is made equal to the transversearea encompassed by the outer peripheral surface of the mandrel 90.Accordingly, forces due to fluid pressures below and inside the mandreltending to elevate it are balanced or cancelled by the same pressureacting downwardly on the piston 126. The purpose of this arrangement isto prevent the influence of fluid pressure changes that occur during adrill stem test from affecting the longitudinal relative positions ofthe mandrel 90 and the housing 91, and to eliminate changes in freepoint indications at the surface due to such pressure changes.

An additional extension of the mandrel 90 has an annular piston 141 thatis sealed within a cylinder section 142 of the housing 91 and encloses,together with an inwardly extending shoulder 143, an atmospheric chamber144 above the piston 141. The lower face of the piston 141 is exposed tothe hydrostatic head of fluids in the annulus by ports 145, and ofcourse the upper face of the shoulder 143 is exposed to the samepressures. A seal 146 prevents fluid leakage between the lower end ofthe mandrel 90 and the housing 91, and a seal 147 prevents leakage intothe chamber 144. The purpose of this arrangement is to provide a biasforce that will assist in elevating the mandrel 90 once it has beenlowered. Upon lowering, a force due to the difference between thehydrostatic pressure of well fluids in the annulus and the lesserpressure in the chamber 144 acts in an upward direction on the mandrel90. Moreover, an identical force acts downwardly on the shoul der 143and is transmitted by the housing 91 to the tools therebelow to aid inretaining a packer seat and the packer bypass closed. The presence ofthe bias force will ensure that the mandrel 90 will move upwardly duringa sequence of test tool manipulations, independently of the movement ofother sliding joints in the system.

The lower end of the tester housing 91 is connected by a threaded pin150 to the inner mandrel of the lower balanced slip joint 29 ofidentical construction to the slip joint 23 previously described withreference to FIG. 3. The function of the lower slip joint 23 is toensure that movements that may occur due to operation of the tester 27do not disturb the packer 28. Moreover, the relative movement inherentin the slip joint 23 will provide a clearly evident free point at thesurface as an indication of the operating position of the tools as willbe more fully described.

The packer 28 can be any type of weight set packer having slips toanchor against movement and an internal bypass valve to equalizepressures at the end of the test. The details of such a packer are wellknown to those skilled in this art, and one example is shown in U.S.Pat. No. 3,399,729, McGill, issued Sept. 3, 1968. Basically, the packercomprises an inner mandrel telescopically disposed within an outerhousing that carries expansible packing elements and an expander. A dragassembly having friction blocks that frictionally engage the casing ismounted on the mandrel and carries normally retracted slips. A pin onthe drag assembly follows in a Jay-slot on the mandrel and functions toeither lock the packer parts in running and retrieving positions, or torelease the parts so that the slips can be shifted outwardly by theexpander into gripping contact with the casing and the packing can beexpanded into sealing contact with the casing. A sleeve that carries thepacking elements is laterally spaced relative to the mandrel to providea fluid bypass extending between locations in communication with thewell bore above and below the packing elements. The bypass is closed bymoving the mandrel downwardly until a valve head engages the valve seat.

In operation, the string of tools previously described are lowered intothe well through the wellhead and the packer 28 is disposed at apreselected depth. The tester 27 is closed and the pipe strings 16 and24are either empty of fluids, or a water cushion can be placed in thestring 24 above the tester. In either event, the bore of the pipeprovides a low pressure region with respect to the pressure of fluids inthe formation to be tested. The packer 28 is set to isolate the testzone by suitable manipulations of the pipe strings l6 and 24 and thenlowering the pipe to apply weight to the packer. The slips are shiftedoutwardly by an expander cone and the weight of the pipe string causescompressive force to be applied to the packing elements, resulting inexpansion thereof into sealing contact with the well bore wall. Thelanding flange is properly located in the pipe string 16 and withrespect to the total length of the pipe and equipment in the well boreand the relative travel of the slip joints 23 and 29 so that when theflange is landed to suspend the upper string 16 from the wellhead 12,the slip-joint associated with the combination tool 22 is in tension,but both of the compensating slip joints 23 and 29 are fully closed. Asthe slip joints close, the entire weight of the drill collar string 24is imposed on the tester 27 and on the packer 28. The weight issufficient to set the packer 28 as previously described to pack off thezone to be tested, and to force the tester mandrel 90 downwardly withinthe housing 91. The retarding action of the metering sleeve 103 withinthe tester 27 insures that the packer 28 is set and its bypass closedbefore the test ports 119 have an opportunity to be opened up to fluidflow.

When the tester mandrel 90 reaches the end of its downward travel (indexpin 93 at point B in FIG. 4C), the valve seals I12 and 133 aredisengaged from the valve seats 114 and 115 and the low pressure regionwithin the pipe string 24 is communicated with the well bore zone belowthe packer 28. If the formations adjacent the casing perforations (notshown) can do so, they will produce fluids which will flow into the pipestring 24. The tester valve is left open for a period of time sufficientto permit a complete drawdown of pressure, then the valve is closed topermit recordal of pressure build-up data. The valve is closed by firstelevating and then lowering the pipe strings 16 and 24. As the pipe iselevated, the rig weight indicator will show a first free pointindication as the slip joint 23 extends, then the weight values willcontinue to climb. A second free point indication should be seen as thetester mandrel 90 is raised within the housing 90. In any event, anextensive free point indication will be given as the lower slip joint 29extends. At least when this latter free point is seen, the operator canimmediately release the brake and lower the pipe again. When the landingflange 20 again seats in the wellhead 12, the slip joints 23 and 29 willagain be closed. so that the weight of the drill collars 24 is imposedon the tools therebelow. As the mandrel 90 moves downwardly the secondtime, the projections 97 on the index sleeve 92 engage the lugs 98 onthe mandrel 90 to stop the mandrel short of open position, correspondingto position D in FIG. 4C. The tester 27 is now shut-in and is left inthat condition for the period of time desired to obtain a pressurebuild-up data. During such time, the weight of the drill collar string24 is being applied to the tools to ensure that the packer 28 remainsseated. Additional flow and shut-in periods can be undertaken as manytimes as desired using the sample pipe string manipulations. Each timethe tester mandrel is moved downwardly within the housing 91, thehydrostatic pressure of fluids in the annulus acts upwardly on the lowerface of the bias piston 141 and produces an upward force on the mandrel90 that will tend to return the mandrel to its upper position. Thisforce ensures that when the pipe strings 16 and 24 are lifted at thevessel 10 to cycle the tester 27, upward movement of the mandrel 90 willoccur before the free point of the lower compensating slip joint 29 isindicated at the surface. Thus, regardless of whether a free point isseen for the tester 27 there is positive assurance that the tester isoperating properly.

Since the tester 27 and the slip joints 23 and 29 are balanced withrespect to pressure changes that occur within these tools during a drillstem test, the various free points should remain substantially the sameduring a repetitive sequence of operations. Accordingly, the variousfree point values provide positive surface indications of the operationof the tools.

To terminate the test, the pipe strings 16 and 24 are lifted at thevessel 10 and the lifting continued after the operator sees the freepoint for the lower slip joint 29. As the mandrel of the packer 28 ispulled upwardly, the bypass is opened so that fluid pressures onopposite sides of the packer are equalized. As the end-wise compressiveforce is relieved from the packing elements they will inherentlyretract. The slips are moved away from the casing wall, and the entirestring of tools can be retrieved to the surface.

In the event that the pipe string 16 should be severed for some reasonbelow the wellhead assembly 12, the lower part of the broken pipe willdrop and cause the slip joint section 35 of the tool 22 to close. As themandrel 37 telescopes completely within the housing 38, the lower end ofthe mandrel engages the valve sleeve 53 and pushes it downwardly intospanning relation with the ports 56. The valve sleeve 53 together withthe upwardly closing check valve 64 function to shut-in the pipe stringsand kill the well.

Since certain modifications or changes may be made in the disclosedembodiment of the present invention without departing from the inventiveconcepts involved, it is the aim of the appended claims to cover allsuch modifications and changes falling within the true spirit and scopeof the present invention.

We claim:

1. A method of testing earth formations traversed by an offshore wellbore with test equipment suspended by a pipe string from a floatingvessel, said test equipment including a packer and a tester and slipjoints disposed in the pipe string above and below the tester, saidtester being opened and closed to fluid flow by a sequence of upward anddownward movements, comprising the steps of: positioning the equipmentinto the well bore and setting the packer to isolate the interval offormations to be tested; lowering the pipe string to close the slipjoints and to open the tester; flowing fluid from the formations for aperiod of time; raising the pipe string to close the tester and shut inthe formation; during said raising step, observing a first indication atthe surface that the upper slip joint is extending and a secondindication that the lower slip joint is extending; upon observing saidsecond indication, lowering the pipe string to close both slip joints;and applying pipe weight to the tester and to the packer whilemaintaining the tester in a closed condition.

2. A method of testing earth formations traversed by an offshore wellbore with test equipment suspended by a pipe string from a floatingvessel, said test equipment including a packer adapted to isolate aninterval of the well bore to be tested, said tester being opened andclosed to fluid flow by vertical extensive and contractive movement toalternately flow and shut in the formations, said pipe string includingan upper section and a lower section coupled together by a slip joint,comprising the steps of: positioning the equipment in the well bore andsetting the packer above said interval; closing the slip joint bylowering said upper section and then suspending said upper section inthe well bore from a preselected point in said upper section applyingthe weight of said lower section to cause contractive movement of thetester to open the tester and flow formation fluids into the pipestring; raising the upper section to extend the slip joint and providinga surface indication of the extension of said slip joint; raising bothsections of the pipe string to cause extensive movement of the tester toclose the tester and shut-in formations and providing a surfaceindication of the extension thereof; upon observing said indication ofextension of said tester, lowering said pipe string sections to closesaid slip joint and apply the weight of said lower section to the testerwhile maintaining the tester in a closed condition; and again suspendingsaid upper section in the well bore from the same preselected pointtherein.

3. A method of testing earth formations traversed by an offshore wellbore with test equipment suspended by a pipe string from a floatingvessel, said test equipment including a tester and a packer coupledtogether by a first slip joint, said pipe string including an uppersection and a lower section coupled together by a second slip joint,said tester being opened and closed to fluid flow by upward and downwardmovement, comprising the steps of: positioning the equipment in the wellbore and setting the packer at a predetermined elevation therein;closing both the lower and the upper slip joints and then suspending theupper section of the pipe string in the well bore from a preselectedpoint in said upper section; applying the weight of the lower section ofthe pipe string to the tester to open the tester and flow formationfluids into the pipe string; raising the upper section of the pipestring to extend the upper slip joint and providing a surface indicationof extension of said upper slip joint; raising both sections of the pipestring to close said tester and to extend said lower slip joint;providing a surface indication of extension of said lower slip joint;upon observing said indication of extension of said lower slip joint,lowering said pipe string sections to close the slip joints and againapply the weight of the lower section of the pipe string to the testerand packer while maintaining said tester in a closed condition; andagain suspending said upper section of the pipe string in the well boreat the same preselected point therein.

1. A method of testing earth formations traversed by an offshore wellbore with test equipMent suspended by a pipe string from a floatingvessel, said test equipment including a packer and a tester and slipjoints disposed in the pipe string above and below the tester, saidtester being opened and closed to fluid flow by a sequence of upward anddownward movements, comprising the steps of: positioning the equipmentinto the well bore and setting the packer to isolate the interval offormations to be tested; lowering the pipe string to close the slipjoints and to open the tester; flowing fluid from the formations for aperiod of time; raising the pipe string to close the tester and shut inthe formation; during said raising step, observing a first indication atthe surface that the upper slip joint is extending and a secondindication that the lower slip joint is extending; upon observing saidsecond indication, lowering the pipe string to close both slip joints;and applying pipe weight to the tester and to the packer whilemaintaining the tester in a closed condition.
 2. A method of testingearth formations traversed by an offshore well bore with test equipmentsuspended by a pipe string from a floating vessel, said test equipmentincluding a packer adapted to isolate an interval of the well bore to betested, said tester being opened and closed to fluid flow by verticalextensive and contractive movement to alternately flow and shut in theformations, said pipe string including an upper section and a lowersection coupled together by a slip joint, comprising the steps of:positioning the equipment in the well bore and setting the packer abovesaid interval; closing the slip joint by lowering said upper section andthen suspending said upper section in the well bore from a preselectedpoint in said upper section ; applying the weight of said lower sectionto cause contractive movement of the tester to open the tester and flowformation fluids into the pipe string; raising the upper section toextend the slip joint and providing a surface indication of theextension of said slip joint; raising both sections of the pipe stringto cause extensive movement of the tester to close the tester andshut-in formations and providing a surface indication of the extensionthereof; upon observing said indication of extension of said tester,lowering said pipe string sections to close said slip joint and applythe weight of said lower section to the tester while maintaining thetester in a closed condition; and again suspending said upper section inthe well bore from the same preselected point therein.
 3. A method oftesting earth formations traversed by an offshore well bore with testequipment suspended by a pipe string from a floating vessel, said testequipment including a tester and a packer coupled together by a firstslip joint, said pipe string including an upper section and a lowersection coupled together by a second slip joint, said tester beingopened and closed to fluid flow by upward and downward movement,comprising the steps of: positioning the equipment in the well bore andsetting the packer at a predetermined elevation therein; closing boththe lower and the upper slip joints and then suspending the uppersection of the pipe string in the well bore from a preselected point insaid upper section; applying the weight of the lower section of the pipestring to the tester to open the tester and flow formation fluids intothe pipe string; raising the upper section of the pipe string to extendthe upper slip joint and providing a surface indication of extension ofsaid upper slip joint; raising both sections of the pipe string to closesaid tester and to extend said lower slip joint; providing a surfaceindication of extension of said lower slip joint; upon observing saidindication of extension of said lower slip joint, lowering said pipestring sections to close the slip joints and again apply the weight ofthe lower section of the pipe string to the tester and packer whilemaintaining said tester in a closed condition; and again suspending saidupper seCtion of the pipe string in the well bore at the samepreselected point therein.